Transcript Proxy Climate Data - University of Texas at Austin

Lecture 17
Tectonic-scale Climate Change
Greenhouse/Icehouse Earth (Part II, p. 84-85; Ch. 4, p. 86-91)
No ice sheets on land
Ice sheets on land
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Ice House
Geologic Time Scale
Tectonic-scale Climate Change (Ch. 5, p. 103-112)
Hundreds of millions of years
Plate tectonics and drift concentrated continents at higher latitudes
allowed for more ice cover, which reflected more sunlight and
created a positive feedback to cause greater cooling.
Tectonic-scale Carbon Dioxide Fluctuations (p. 91-99; p. 103121)
Seafloor spreading leads to increased
periods of volcanic degassing of CO2,
which causes warming.
Higher temperatures leads to increased
weathering, which will remove CO2
from the atmosphere and reverse
warming in a negative feedback loop.
Earth’s Climate History in the Last 550 Myr
1.
2.
3.
Over the past 550
Myr, three Icehouse
periods (430, 325-240,
35-0 Myr ago).
For most of the last
550 Myr or the
earth’s entire history,
the climate was much
warmer than today.
Tectonic-scale climate
change is caused by
plate tectonics
Land/ocean positions and sizes
Ocean floor spreading/CO2 increase
Mountain building (uplift) &
weathering / CO2 decrease
4.
Part II p. 82-83; Ch. 4, 5, 6, 7
Other causes.
Chemical weathering (chemical breakdown of
minerals or rocks)
Carbonic acid
Examples:
(Calcite)
(calcium ions)
Limestone + carbon dioxide + water  dissolved ions + bicarbonate
CaCO3
+ CO2
+ H2O  Ca2+
+ 2HCO3-
The World 100 Myr Ago (p. 129-137)
Flooding of The
Continents
Cretaceous  Greenhouse Earth
Warm period of dinosaurs
Evidence
No record of glaciers or polar ice caps
Faunal/floral zone latitudinal shift
Isotopes  warmer oceans
Environments shift with near tropics to the poles
Oceans/Atmosphere/Land Features
Sea level 100-200 m higher because of no polar ice caps
Intense storms (hurricanes) because of warmer waters
Stronger hydrologic cycle
Less wind because lower T and P gradients globally
More plants, more flowers; extent of dry land reduced
by flooding
Causes
Sun-Earth relationship
Land-sea configuration
More oceans in low latitudeslower albedo
More land in high latitudesmore plants
More CO2 in atmosphere (4-8 x)
1. The last time atmospheric CO2 concentrations and temperatures were much
higher than today was in the age of dinosaurs.
2. Agriculture revolution began 10,000 years ago.
3. Human population explosion in the past 100 years. Today: 6 billion
6 5 million
years
10 million
PRESENT
55 million years
years
3.5 Million years
18,000 years
1 Million years
10,000 years
230,000 years
1,000 years
100,000 years
The only mammals living at this time were small rodents.
What about Texas?
Sea levels were much higher than today, and Texas
was mostly under water
Climate change was one important reason that the
dinosaurs disappeared.
Global Cooling Trend in the Last 55 Myr
Ch. 7
Causes: decrease in ocean
floor spreading rate;
uplift weathering;
ocean heat transport
through gateways;
ice-albedo feedbacks
Cooling from leaf outline
Cooling from ocean isotopes
Decrease in spreading rate